Some MM tests use memalign() to allocate memory. However, the resulting memory area may unexpectedly merge with an adjacent VMA, causing tests that inspect it through /proc/self/smaps to fail.
Eliminate this potential source of test flakiness by introducing alloc_isolated_mem(), which places guard regions before and after the allocated area to prevent unexpected VMA merging. Replace memalign() with this helper and use the helper in softdirty_supported() instead of mmap(). Link: https://lore.kernel.org/all/apHDdRSr59mva3ey@lucifer/ [0] Suggested-by: Lorenzo Stoakes (ARM) <[email protected]> Signed-off-by: Yeoreum Yun <[email protected]> --- tools/testing/selftests/mm/pagemap_ioctl.c | 18 +++--- tools/testing/selftests/mm/soft-dirty.c | 6 +- tools/testing/selftests/mm/split_huge_page_test.c | 8 +-- tools/testing/selftests/mm/vm_util.c | 67 +++++++++++++++++++++-- tools/testing/selftests/mm/vm_util.h | 2 + 5 files changed, 81 insertions(+), 20 deletions(-) diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/selftests/mm/pagemap_ioctl.c index eadc7159ca5b..7ed5b8fb3b25 100644 --- a/tools/testing/selftests/mm/pagemap_ioctl.c +++ b/tools/testing/selftests/mm/pagemap_ioctl.c @@ -792,9 +792,9 @@ void *gethugepage(int map_size) int ret; char *map; - map = memalign(hpage_size, map_size); + map = alloc_isolated_mem(hpage_size, map_size); if (!map) - ksft_exit_fail_msg("memalign failed %d %s\n", errno, strerror(errno)); + ksft_exit_fail_msg("alloc_isolated_mem failed %d %s\n", errno, strerror(errno)); ret = madvise(map, map_size, MADV_HUGEPAGE); if (ret) @@ -856,7 +856,7 @@ int hpage_unit_tests(void) /* 4. only middle page written */ wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); map = gethugepage(map_size); wp_init(map, map_size); wp_addr_range(map, map_size); @@ -871,7 +871,7 @@ int hpage_unit_tests(void) "%s only middle page written\n", __func__); wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s all new huge page must be written\n", __func__); ksft_test_result_skip("%s all the huge page must not be written\n", __func__); @@ -898,7 +898,7 @@ int hpage_unit_tests(void) vec[0].start == (uintptr_t)(map + map_size/2), "%s clear first half of huge page\n", __func__); wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s clear first half of huge page\n", __func__); } @@ -927,7 +927,7 @@ int hpage_unit_tests(void) "%s clear first half of huge page with limited buffer\n", __func__); wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s clear first half of huge page with limited buffer\n", __func__); @@ -955,7 +955,7 @@ int hpage_unit_tests(void) ksft_test_result(ret == 1 && LEN(vec[0]) == vec_size/2, "%s clear second half huge page\n", __func__); wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s clear second half huge page\n", __func__); } @@ -988,7 +988,7 @@ int hpage_unit_tests(void) "%s get half huge page\n", __func__); wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s get half huge page\n", __func__); ksft_test_result_skip("%s get half huge page\n", __func__); @@ -1702,7 +1702,7 @@ int main(int __attribute__((unused)) argc, char *argv[]) wp_addr_range(map, hpage_size); base_tests("Huge page testing:", map, hpage_size, 0); wp_free(map, hpage_size); - free(map); + free_isolated_mem(map, hpage_size); } else { base_tests("Huge page testing:", NULL, 0, 1); } diff --git a/tools/testing/selftests/mm/soft-dirty.c b/tools/testing/selftests/mm/soft-dirty.c index 5f278913c4d7..b6fad38c8bee 100644 --- a/tools/testing/selftests/mm/soft-dirty.c +++ b/tools/testing/selftests/mm/soft-dirty.c @@ -92,9 +92,9 @@ static void test_hugepage(int pagemap_fd, int pagesize) if (!hpage_len) ksft_exit_fail_msg("Reading PMD pagesize failed"); - map = memalign(hpage_len, hpage_len); + map = alloc_isolated_mem(hpage_len, hpage_len); if (!map) - ksft_exit_fail_msg("memalign failed\n"); + ksft_exit_fail_msg("alloc_isolated_mem failed\n"); ret = madvise(map, hpage_len, MADV_HUGEPAGE); if (ret) @@ -130,7 +130,7 @@ static void test_hugepage(int pagemap_fd, int pagesize) ksft_test_result_skip("Test %s huge page allocation\n", __func__); ksft_test_result_skip("Test %s huge page dirty bit\n", __func__); } - free(map); + free_isolated_mem(map, hpage_len); } static void test_mprotect(int pagemap_fd, int pagesize, bool anon) diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c index 4bbad892bc57..7a600131f7f0 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -154,7 +154,7 @@ static char *allocate_zero_filled_hugepage(size_t len) char *result; size_t i; - result = memalign(pmd_pagesize, len); + result = alloc_isolated_mem(pmd_pagesize, len); if (!result) { printf("Fail to allocate memory\n"); exit(EXIT_FAILURE); @@ -217,7 +217,7 @@ static void split_pmd_zero_pages(void) one_page = allocate_zero_filled_hugepage(len); verify_rss_anon_split_huge_page_all_zeroes(one_page, nr_hpages, len); ksft_test_result_pass("Split zero filled huge pages successful\n"); - free(one_page); + free_isolated_mem(one_page, len); } static void split_pmd_thp_to_order(int order) @@ -226,7 +226,7 @@ static void split_pmd_thp_to_order(int order) size_t len = 4 * pmd_pagesize; size_t i; - one_page = memalign(pmd_pagesize, len); + one_page = alloc_isolated_mem(pmd_pagesize, len); if (!one_page) ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno)); @@ -261,7 +261,7 @@ static void split_pmd_thp_to_order(int order) ksft_exit_fail_msg("Still AnonHugePages not split\n"); ksft_test_result_pass("Split huge pages to order %d successful\n", order); - free(one_page); + free_isolated_mem(one_page, len); } static void split_pte_mapped_thp(void) diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c index dc62ce84e143..159d627ae3b0 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -19,6 +19,11 @@ #define KPAGEFLAGS_PATH "/proc/kpageflags" #define MAX_NR_ORDERS 20 +#define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1))) +#define ALIGN_PTR(p, a) ((typeof(p))ALIGN((unsigned long)(p), a)) +#define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) == 0) +#define PTR_ALIGNED(p, a) (IS_ALIGNED((unsigned long)(p), a)) + unsigned int __page_size; unsigned int __page_shift; @@ -514,6 +519,61 @@ int64_t allocate_transhuge(void *ptr, int pagemap_fd) return -1; } +void *alloc_isolated_mem(size_t align, size_t size) +{ + char *ptr, *guard, *addr_align; + size_t map_size, guard_size, page_size = psize(); + size_t padding; + + if (__builtin_popcountll((unsigned long)align) > 1) + return NULL; + + align = (align > page_size) ? align : page_size; + guard_size = page_size; + size = ALIGN(size, page_size); + map_size = size + align + guard_size; + + ptr = mmap(NULL, map_size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (ptr == MAP_FAILED) + return NULL; + + addr_align = PTR_ALIGNED(ptr, align) ? ptr + align : ALIGN_PTR(ptr, align); + padding = addr_align - guard_size - ptr; + if (padding) { + munmap(ptr, padding); + map_size -= padding; + ptr += padding; + } + + guard = ptr; + if (mprotect(guard, guard_size, PROT_NONE)) + goto err_out; + + guard = addr_align + size; + if (mprotect(guard, guard_size, PROT_NONE)) + goto err_out; + + padding = (ptr + map_size) - (guard + guard_size); + if (padding) + munmap(guard + guard_size, padding); + + return addr_align; + +err_out: + munmap(ptr, map_size); + return NULL; +} + +void free_isolated_mem(void *addr, size_t size) +{ + int guard_size, page_size = psize(); + + guard_size = page_size; + munmap((char *)addr - guard_size, + guard_size * 2 + ALIGN(size, page_size)); +} + int pageflags_get(unsigned long pfn, int kpageflags_fd, uint64_t *flags) { size_t count; @@ -618,13 +678,12 @@ bool softdirty_supported(void) const size_t pagesize = getpagesize(); /* New mappings are expected to be marked with VM_SOFTDIRTY (sd). */ - addr = mmap(0, pagesize, PROT_READ | PROT_WRITE, - MAP_ANONYMOUS | MAP_PRIVATE, 0, 0); - if (addr == MAP_FAILED) + addr = alloc_isolated_mem(pagesize, pagesize); + if (!addr) ksft_exit_fail_msg("mmap failed\n"); supported = check_vmflag(addr, "sd"); - munmap(addr, pagesize); + free_isolated_mem(addr, pagesize); return supported; } diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h index f19bd17817e5..ce1da9a55310 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -95,6 +95,8 @@ bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size); bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size); int64_t allocate_transhuge(void *ptr, int pagemap_fd); +void *alloc_isolated_mem(size_t align, size_t size); +void free_isolated_mem(void *addr, size_t size); int pageflags_get(unsigned long pfn, int kpageflags_fd, uint64_t *flags); int gather_folio_orders(char *vaddr_start, size_t len, int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders); -- 2.43.0
